Molecular dynamics study of the effect of structural defects, impurities, and the presence of a shell on the melting temperature of metallic nanoparticles

Using the molecular dynamics method, a study was conducted on the influence of structural defects, carbon and hydrogen impurities, as well as the presence of a shell of another metal, on the melting temperature of metallic nanoparticles. It was shown that the melting point of metallic nanoparticles could be controlled not only by varying the size of the nanoparticle but also by changing the concentration of structural defects, introducing impurities, and creating a shell of another metal with specially selected characteristics. An increase in the concentration of structural defects, grain boundaries, dislocations, disclinations, etc., leads to a decrease in the melting temperature. Moreover, the melting temperature of a nanoparticle linearly decreases with an increase in the excess energy caused by the presence of defects. The introduction of impurity atoms of carbon and hydrogen also leads to a decrease in the melting point, with carbon having a greater effect on the reduction of the melting temperature of nickel nanoparticles compared to hydrogen, due to its larger dilatational effect. It was found that the melting point of the nanoparticle core could be controlled by selecting the shell material. With close lattice parameter values, but with a relatively higher binding energy of the shell metal, the melting temperature of the core increases, otherwise it decreases.